IPA: //ʌnˈæmplɪfaɪd//
KK: /ʌnˈæmplɪfaɪd/
Not increased in volume or strength; refers to sound that is natural and not enhanced by electronic means.
The singer performed an unamplified version of the song in the small café.
Unamplified → It is formed from "un-" (meaning not) and "amplified" (from Latin "amplificare", meaning to enlarge or increase). The word "unamplified" means not enlarged or increased, referring to something that has not been made larger or more intense.
Think of 'not' ('un-') making something 'larger' ('amplified') — that's why unamplified means it hasn't been made larger.